The closed-loop Regenerative.RTM. air system was invented more than twenty-five (25) years ago by Mr. Bernard W. Young, as is evidenced by U.S. Pat. Nos. 3,512,206 and 3,545,181 granted on May 19 and Dec. 8, 1970, respectively. Tymco, Inc. of Waco, Tex. has manufactured closed-loop Regenerative.RTM. air sweepers for more than twenty-five years, and each uses the force of a high velocity controlled jet of air created by a powerful blower to blast down and across a pickup head onto pavement and into cracks thereof forcing up into the air stream of the pickup head packed-on heavy debris and fine dust particles. The debris-laden air stream is pulled into a large hopper where the air loses velocity and larger debris falls to the bottom. A screen at the top of the hopper prevents items, such as leaves, paper, cans, rocks and large pieces of debris from leaving the hopper and entering a centrifugal dust separator. The centrifugal dust separator spins the air along a curved wall of a centrifugal separator chamber until small size dust particles are skimmed off into the hopper and substantially clean air is returned to the blower to continue the closed-loop air cycle of the Regenerative.RTM. air sweeper. This closed loop system substantially prevents dirty air from being undesirably exhausted into the environment.
Such Tymco Regenerative.RTM. air sweepers are highly efficient under dry conditions and are also relative efficient even under rainy or wet conditions. Mechanical sweepers utilizing brooms and vacuum sweepers utilizing both brooms and vacuums tend to clog and/or smear while the Regenerative.RTM. air sweeper continues to efficiently clean under such rainy or wet conditions which means cleaning schedules can be accurately maintained and fulfilled.
While such Regenerative.RTM. air sweepers have performed admirably over the years and were originally intended for use in hazardous environments, applications have grown to include virtually all dustless operations in such environments as tunnels, building interiors and most any other uses where water for dust suppression is not an option (cement plants, freezing climates, etc.) The Environmental Protection Agency (EPA) has also expanded its restrictions concerning dustless operation and a need has arisen for a truly substantially "dustless" Regenerative.RTM. air sweeper.
A truly substantially "dustless" Regenerative.RTM. air sweeper has become highly desirable due to more stringent requirements of the EPA, and sensitivities involved in substantially dustless operation in such environments as noted immediately heretofore, particularly should dust be laden with water and/or moisture.
Several efforts have been made toward achieving dustless debris collection, as is evidenced by U.S. Pat. Nos. 4,870,489; 4,006,511 and 4,457,043 issued respectively on Mar. 11, 1975; Feb. 8, 1977 and Jul. 3, 1984. Each of these patents discloses a sweeping machine which desirably seeks to prevent dust-entrained air from being exhausted to atmosphere. For example, in U.S. Pat. No. 4,457,043 air is drawn from a main mouthpiece through a suction pipe into a coarse separator arranged in front of a cyclone separator with air being recycled through a fan and another conduit to the main mouthpiece. A portion of the air stream from the fan is diverted to another separator through which air is exhausted by a separate fan. The latter prevents the overall system from being truly "closed" because a substantial portion of the air and any entrained debris beyond the separator is evacuated into atmosphere by the associated evacuation fan. A similar auxiliary blower associated with the mobile street sweeper of U.S. Pat. No. 4,006,511 prevents the system from being essentially "closed." However, these and other similar patents, such as U.S. Pat. No. 3,870,489, reflect common usage of bag house filtering units and/or cyclone filtering units associated with street sweepers, though none in association with a Regenerative.RTM. air sweeper which maintains substantially 100 percent air flow through its closed-loop air system absent debris being forcefully or otherwise exhausted to atmosphere.